1. Field of the Invention.
The present invention relates to self-propelled slip form paving machines.
2. Prior Art.
The prior art, slip form paving machines of various kinds have been developed. For example, U.S. Pat. No. 3,223,006 shows a machine for forming intergal sidewalks and curbs which uses a slip form for the formation of these sidewalks and curbs. Other apparatus in the art is exemplified by a curb forming machine shown in the patent to C. Jennings, U.S. Pat. No. 3,053,156 which has a pair of wheels at the rear thereof that can be laterally moved across the width of the machine for accommodating different form locations and cross section shapes.
Also, automatic controls for operating various grading and paving machines are known, and these controls have been utilized for following a string line or reference level line. Two patents relating to automatic steering and automatic control apparatus issued to Honeywell, Inc., Minneapolis, Minnesota are U.S. Pat. No's. 3,210,710 and 3,258,082.
Further there are paving machines on the market which incorporate vertically adjustable frames for forming concrete members at different heights, for example highway median barrier walls or curbs and gutters. Such machines do include drive wheels which are individually powered from hydraulic motors, and which are mounted on single hinged arms for the raising and lowering of the frame. These swinging arms are relatively long and require extremely heavy members to withstand the loads involved. The steering axis of the wheel on the arms also changes from the vertical as the frame is lifted.
In other paving machines, at least four wheels are used for supporting the machine, and the wheels are mounted on transversely adjustable members so that the positioning of the wheels is changed when different forms are used.